Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron

Definitions

• the present invention relates to high strength low alloy steels and, more particularly, to high strength steels for welding structural services.
• the low carbon steel possesses a yield point of more than 70 kg./mrn. and superior toughness and has been proved in reduced hardenability in welding and decreased crack sensitivity.
• the invention also contemplates providing a unique steel particularly adapted to be employed in the Welding structure.
• the present invention contemplates the manufacture of steels heat-treated with quenching of adapting liquids (containing water), gases (containing air), or mixtures of above media at a temperature from AC point to 1050 C. and then with tempering at a temperature of less than AC point.
• the steels of the present invention are composed of the following constituents:
• Carbon is one of the more potent and more economical strengthening elements. It is well known that carbon has the strongest influence upon hardenability of weld zone. Accordingly, it is to be desired that carbon content be low as much as possible. Carbon of more than 0.05%, however, is practical from this point of steel making. The upper limit of carbon content, which is 0.15%, is recommended, owing to the need of making 0.01 to 0.03% Nb solute at a quenching temperature of 900 C. to 1000 C., so as to cause Nb-carbide after tempering treatment.
• Niobium content must be determined in consideration of carbon content. According to our experimentations, it is shown that Nb of more than 0.05% scarcely contributed to strength steel. Also, it is impossible to obtain the required strength when Nb content is less than 0.005%
• the suitable Nb content in the present invention consists in the range of 0.005 to 0.05%.
• Manganese of 0.50% which is the lower limit is adopted in consideration of this point of steel making and of hotworkability. Also, 1.60% Mn which is the upper limit is determined in consideration of weldability.
• 0.15% to 0.7% molybdenum possibly causes strength of steel to markedly increase. However, when the content is more than 0.7%, weldability of steel is spoiled and when the content is less than 0.15 strength of steel is harmed.
• titanium is a useful element for improving hardenability of steel and for increasing strength of steel owing to precipitation of Ti-carbide in the tempering treatment stage.
• Nitrogen content has a serious influence on combination of Nb-Ti-B which is the main point in the present invention.
• the content must be limited within the range in which it is impossible to form its nitride. More than 0.007% nitrogen harms toughness of steel, owing to the formed Ti-nitride and causes Ti-carhide, which is effective for strength of steels 4 Examining the above-mentioned values, it is understood that maximum hardness in taper hardness test is far lower than the maximum value required by the same kind of high strength steel, such as Hv$430 in Japanese WES Standard. This fact shows that hardness of welding zone to decrease.
• Nitrogen content of the lower limit is 0.002% is markedly lowered according to keeping yield strength according to a restriction of steel making process. of 70 kg.mm. by means of a suitable combination of II! the range of the above-mentioned C l C Nb+Ti+B and at the same time main alloying elements, position, the following range is recommended as preferred such as C, Mn, Ni, Cr, Mo and the like, are far less than values: ordinary high-strength steels.
• High strength low alloy steels composed of 0.05 to As mentioned above, the present invention steel is com- 015% to t0 L posed of alloying of a small quantity of components, and to 150% Mn, and t0 5 t 080% demonstrates yield strength of more than 70 kg./mm. Cu, to 100% to (110% 0-002 to superior toughness and excellent weldability according to N, 0-005 to 0.04% Nb, 0.0005 to 0-00 heat treatment of quenching mother steel from more than 0-005 to (105% T1 and havlhg a V 4 Strength Q more 4C temperature and then of tempering at more than than Q' and POSSeSSIhg sufficleht weldahlllty- 5 C.
• High strength low alloy steels in accordance with The following Table 1 shows examples of the present inclalm 1h Whlch the alloying ingredients wmprise vention steel.
• steels are the presto 012% c, to 050% Si, L00 t0 ent invention steels.
• H to K which are out of 020 to 040% Cu, to 050% 0420 to 0360% the range of components based on the present invention, 04010 to 0'050% 0.005 to (105% 0- to these steels are shown in comparison with the present in- 0.03 Ti, 0.001 to 0.003% B, up to 0.005% N, vention steel.
• L steel is an ordinary high-strength low alloy 3.
• High strength low alloy steel in accordance with claim 2 wherein the steel following heat treatment is 5 quenched at a temperature from AC to 1050 C. and 3,368,887 2/1968 Clark 75-128R then is tempered at less than AC temperature.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=11555988

Family Applications (1)

Country Status (5)

Cited By (14)

Families Citing this family (6)

• 1969
  • 1969-01-22 SE SE819/69A patent/SE344215B/xx unknown
  • 1969-01-22 GB GB3547/69A patent/GB1210795A/en not_active Expired
  • 1969-01-22 FR FR6901072A patent/FR2000542A1/fr not_active Withdrawn
  • 1969-01-22 DE DE19691903070 patent/DE1903070A1/de active Pending
  • 1969-01-22 US US802715*A patent/US3592633A/en not_active Expired - Lifetime

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